INFO: task syz-executor0:14004 blocked for more than 120 seconds. Not tainted 4.16.0-rc5+ #352 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D23504 14004 4163 0x00000004 Call Trace: context_switch kernel/sched/core.c:2862 [inline] __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440 schedule+0xf5/0x430 kernel/sched/core.c:3499 schedule_timeout+0x1a3/0x230 kernel/time/timer.c:1777 do_wait_for_common kernel/sched/completion.c:86 [inline] __wait_for_common kernel/sched/completion.c:107 [inline] wait_for_common kernel/sched/completion.c:118 [inline] wait_for_completion+0x415/0x770 kernel/sched/completion.c:139 ucma_destroy_id+0x2c1/0x4c0 drivers/infiniband/core/ucma.c:605 ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1633 __vfs_write+0xef/0x970 fs/read_write.c:480 vfs_write+0x189/0x510 fs/read_write.c:544 SYSC_write fs/read_write.c:589 [inline] SyS_write+0xef/0x220 fs/read_write.c:581 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x453e69 RSP: 002b:00007fa938d8ac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fa938d8b6d4 RCX: 0000000000453e69 RDX: 0000000000000018 RSI: 0000000020000040 RDI: 0000000000000013 RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000672 R14: 00000000006f9b50 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/800: #0: (rcu_read_lock){....}, at: [<00000000362df8b4>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000362df8b4>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000000a73cb19>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4084: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4085: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4086: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4087: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4088: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4089: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4090: #0: (&tty->ldisc_sem){++++}, at: [<00000000c71be986>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000cb290d88>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 800 Comm: khungtaskd Not tainted 4.16.0-rc5+ #352 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x123/0x180 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54